The objective of this research is to study the role of retinyl ester in the mammalian visual cycle. Specifically, we will conduct biochemical analyses to evaluate a retinyl ester hydrolase which catalyses the hydrolysis of retinyl esters in the retinal pigment epithelium. Earlier results have shown that this enzyme is specific for the physiologically important 11- cis isomer and it has a sufficiently high activity to release retinal as precursor of visual pigment chromophore. Many detailed biochemical properties of the enzyme remain to be explored. We propose to further examine the location of this hydrolase in the plasma membrane which is a possible site of the enzyme. We also plan to purify this enzyme and study its activity in its native membrane, in solution and in reconstituted membranes. Our investigation into the utilization of retinyl esters in the eye will provide important information relating to various ocular disorders. One MBRS graduate and one MBRS undergraduate student will participate in the study of the research of visual biochemistry of the eye. Student training will include designing and performing experiments, participation in laboratory meetings, presentation of research in laboratory journal club and at national meetings. Students will also participate int he preparation of research manuscripts and coauthor publication of experimental findings in refereed, scientific journals.